1. Field of the Invention
The present invention relates to a magnetoresistive head and a method of manufacturing the same and a magnetic recording apparatus and, more particularly, a magnetoresistive head used for reading information signals recorded on a magnetic recording medium and a method of manufacturing the same, and a magnetic recording apparatus such as a magnetic disk apparatus, a magnetic card apparatus and a magnetic tape apparatus, having the magnetoresistive head.
2. Description of the Prior Art
In order to put a magnetic head employing magneto-resistance effect to practical use, a magnetoresistance layer (referred to as an MR layer hereinafter) composed of a ferro-magnetic material must respond linearly to a magnetic signal field generated by a recording medium.
A magnetic bias should be applied to the MR layer to attain a linear response of the MR layer. Such magnetic bias is called as a linearization bias. Several approaches have been known as means for applying the linearization bias. As one of the approaches, a soft magnetic layer is arranged near the MR layer to apply the linearization bias thereto. This approach has advantages such as a good bias efficiency and a small shift in a bias point by sense current.
A conventional MR device is disclosed in Patent Application Publication (KOKAI) 63-117310, for example. As shown in FIG. 1, the conventional MR device is constituted.
Referring to FIG. 1, a soft magnetic layer 2, a non-magnetic separating layer 3, and an MR layer 4 are formed on a substrate 1 in that order. They are formed to have their rectangular plane shapes. Two antiferromagnetic films 5a and 5b for controlling magnetic domains of the MR layer 4 are then formed on the MR layer 4 so as to put a sense area A therebetween. Conductive leads 6a and 6b are then formed on the antiferromagnetic films 5a and 5b respectively.
Since, in the magnetic head so constructed above, the MR layer 4 is formed on the outside of both sides of the sense area A of the MR device, the MR layer 4 located near the sense area A also detects the magnetic field generated by the recording medium. Consequently, the sense area A is vaguely defined. This therefor becomes an obstacle to attaning a small distance between tracks of the magnetic recording medium and a high density of the magnetic recording medium. It would be preferable that the sense area A be more distinctly defined by the space between two conductive leads 6a and 6b.
Upon forming layers, the MR layer 4 is magnetized simultaneously with the soft magnetic layer 2 and in the same direction as those of the soft magnetic layer 2. However, the direction of the magnetization of the soft magnetic material is inherently unstable. Therefore, the direction thereof tends to vary by an external magnetic field. As a result, as shown in FIG. 2, a Barkhausen jump which results in an output fluctuation of the MR device is readily caused. The Barkhausen jump appears as a hysteresis loop in part of a characteristic curve of a change in electric resistivity (.rho.) of the MR layer against an external magnetic field (H).
On the contrary, another magnetic head, wherein the MR film 4 is formed to have the substantially same width as that of the track and soft magnetic films with a small magnetoresistance effect are disposed on both sides of the MR film 4, has been proposed in Patent Application Publications (KOKAIs) 4-298809 and 3-30109.
According to this magnetic head, the vague sense area of the MR film is never caused and further the Barkhausen jump is scarcely caused because of the absence of the soft magnetic film.
However, since no mechanism for supplying a linearization bias is provided in the structure of this magnetic head, it is not practical that such magnetic head is adopted as it is. In addition, there is not provided a mechanism for reducing the Barkhausen jump which is caused by instability of the magnetic field of the soft magnetic film disposed in parallel to the MR layer. Besides, since no antiferro-magnetic films exists on both sides of the MR layers, it is not disclosed as a concrete structure how to control magnetic domains (i.e., magnetization directions) of the MR layer.